1. Field of the Invention
The present invention relates to a linear motion guide unit including therein recirculating passages in which rolling elements are allowed to run along the recirculating passages, and separators are each arranged between any two adjoining rolling elements and joined together with each other by means of chain couplers.
2. Description of the Prior Art
Conventionally a linear motion guide unit of the type as shown in FIG. 21 is well-known in which only rolling elements such as balls, rollers and so on are installed in a recirculating passage. The prior linear motion guide unit comprises an elongated track rail 2 having raceway grooves 4 on lengthwise side surfaces thereof, and a slider 1 having raceway grooves 9 confronting the raceway grooves 4 of the track rail 1. The slider 2 fits over and conforms to the track rail 2 for sliding movement with respect to the track rail 2. The slider 2 will move along the track rail 1 by virtue of rolling elements 7 such as balls, which are allowed to run in load raceways 16 defined between the confronting raceway grooves 4 and 9. The track rail 2 has openings 13 boring through from an upper surface 14 to a bottom surface thereof at locations spaced lengthwise from each other. The track rail 2 will be fastened to the mounting base 20, such as a bed, machine base, work table or the like, by screwing bolts through the openings 13 of the track rail 2 into threaded holes in the mounting base 20.
The slider 1 has a carriage 5 movable relatively to the track rail 2, and end caps 6 secured to the opposite ends of the carriage 5, each to each end. Provided on the upper surface of the carriage 5 are openings 19 for mounting the slider 1 to other appliances, parts, chucks, grasping jaws or the like. The end caps 6 are attached on the lengthwise opposing end surfaces of the carriage 5 by means of more than one bolt 25. Both of the carriage 5 and the end caps 6 are made with recesses 10 that are opened downwards such that the carriage 5 and the end caps 6 are allowed to fit over and conform to the track rail 2 for sliding movement relatively to the track rail 2. The carriage 5 is also provided therein with return passages 12 extending in parallel with the raceway grooves 9. The end caps 6 are provided therein with claws for scooping the rolling elements 7 out of the load raceways 16 defined between the confronting raceway grooves 4 and 9, and turnaround passages, given the reference numeral 15 in FIG. 13, for recirculation of the rolling elements 7.
In the linear motion guide unit described earlier, retainer bands 18 are provided in the carriage 5 to hold the rolling elements 7, thereby preventing the rolling elements 7 from falling out of the carriage 5. Bottom seals 8 are secured to the lower surfaces of the carriage 5 and the end caps 6 to thereby close clearances between the track rail 2 and the slider 1. Also mounted on the outside end faces of the end caps 6 are end seals 17, each to each end cap, for keeping sealing function between the track rail 2 and the lengthwise opposing ends of slider 1.
The rolling elements 7 run along the load areas, that is, the load raceway 18 defined between the raceway grooves 4 of the track rail 2 and the raceway grooves 9 of the carriage 5, and then come in the turnaround passages 15 in any one of the end caps 6. The rolling elements 7 further run from the turnaround passages 15 to the return passages 12 that are formed in the carriage 5 in parallel with the load raceway grooves 9. Subsequently the rolling elements 7 return to the load areas of the raceways 16 through the turnaround passages 15 in the other one of the end caps 6. It will be thus understood that the rolling elements 7 may run in a recirculating manner though recirculating passages given the reference numeral 21 in FIG. 13, which are composed of the load raceways 16, turnaround passages and return passages 12, thereby helping ensure the smooth movement of the slider 1 relatively to the track rail 2. Installed on any one of the forward and aft end seals 17 is a grease nipple 11 through which lubricant is supplied into the carriage 5 to lubricate the raceway grooves 4 and 9 along which run the rolling elements 7.
With the conventional linear motion guide units constructed as stated earlier, any separator is interposed between any two adjoining rolling elements to keep the rolling elements against coming into rolling collision with one another, which might cause any contact force opposite in direction. Moreover, various other linear motion guide units have been devised heretofore, which are called the chain-type linear motion guide unit because of their specific construction in which the separators are joined together with each other by endless chains of couplers. Disclosed in Japanese Patent Laid-Open No. 247855/1999 is a linear motion guide unit in which the rolling elements or balls running through a recirculating passage are spaced apart from each other by separators that are each interposed between any two adjoining balls and interconnected with each other through strings in such an individually replaceable manner. Each separator is comprised of a major body made at forward and aft faces thereof with ball-contact surfaces for carrying the associated balls thereon, and webs formed integrally with the major body and extended fore-and-aft along the running direction over the spherical surfaces of the balls, and the webs being each provided therein with channels. The separators arranged in the recirculating passage with being each interposed between any two adjoining balls are interconnected with one another by using a string threading through the channels in the webs.
Further, Japanese Patent No. 2607993 discloses a linear motion guide unit having incorporated with a chain of balls, which is comprised of a series of balls running through a recirculating passage, ball retainers each interposed between any two adjoining balls, and a flexible coupler member for joining together the balls and retainers in a tandem array. The ball retainers are each made concaved at forward and aft faces thereof so as to fit snugly over the associated balls in a manner allowing the ball retainer to move relatively to the associated balls. Thus, a series of balls may be made in an endless form by bending the flexible coupler member in a loop. With the ball chain recited earlier, however, there is some tendency in which the concaved surfaces of the ball retainer, when running through the turnaround, are drawn radially inwardly of a curvature of locus of rolling-contact point between the ball retainer and the associated ball, thus causing much deformation in the ball retainer at the area between the concaved surfaces that are opposite sides of the ball retainer. As a result, there is a possibility that the flexible coupler member might be much subject to deformation at the area between the concaved surfaces because the flexible coupler member is less in thickness at the area between the concaved surfaces.
Disclosed in Japanese Patent Laid-Open No. 89358/1998 is another linear motion guide unit, in which the balls fit in the flexible coupler member with being positioned at regular intervals in tandem along their moving direction. In need of repair or replacement of the ball, any ball may be removed from the coupler member by only pressing out the ball towards any raceway groove of the load raceway where the balls run through there.
Another Japanese Patent Laid-Open No. 351255/1999 discloses a coupler arrangement for a series of rolling elements, which is comprised of a carrier strip of flexible element made therein with a series of openings to accommodate therein rolling elements, and holder elements to keep in position the rolling elements fit in the openings. The carrier strip is composed of sidewise opposing lengthwise edges and traverse sections extending crosswise between the lengthwise edges while the holder elements are attached to the flexible element at the lengthwise edges of the carrier strip. Moreover, a chain-type linear motion rolling bearing arrangement proposed initially is disclosed in Japanese Patent Laid-Open No. 242126/1987, wherein the separators are each interposed between any two adjoining rolling elements to keep the rolling elements against coming into rolling collision with one another during running through the recirculating passage, especially the load raceway, which might cause any contact force opposite in direction. In addition, the coupler means or the chains are provided to join together the separators with each other, thus helping protect the rolling elements from wear owing to the metal-to-metal collision thereof, with the result of improving smooth recirculation property of the rolling elements. With the slider in the linear motion guide unit having therein at least two curvilinear passages or turnarounds where the rolling elements running through the recirculating passage will turn over in moving direction, nevertheless, how smoothly the rolling elements can travel through the turnarounds would be important to the chain-type linear motion guide units. Thus, it remains a major challenge to ensure the smooth run of the rolling elements, each of which is held between the adjacent separators joined together by the coupler chains, at the turnarounds in the end caps.
The present invention is directed to overcoming one or more of the problems as set forth above, and more particular, allowing a combination of rolling elements, separators each interposed between any two adjoining rolling elements and a coupler member joining together the separators with one another to run smoothly through a recirculating passage comprised of linear passages and curvilinear passages, both of which are provided in a slider. To cope with this, according to the present invention, a linear motion guide unit with a separator coupler is provided, in which the separators are each made unchanged in thickness at a limited zone so as to allow a sliding contact point thereof with the associated rolling element to easily swerve radially inwardly of the curvilinear passage when the separator moves through the turnaround, and moreover the coupler member is made in the form of a flexible strip kept substantially constant in cross section throughout the overall length to be bend uniformly with a fixed radius of curvature when moving in the turnaround, the fixed radius of curvature being defined within a desired range.
The present invention is concerned with a linear motion guide unit with a separator coupler, comprising a track rail, a slider movable with respect to the track rail and including therein a recirculating passage composed of a linear passage and a curvilinear passage connected to each other, the recirculating passage having incorporated with rolling elements, separators each interposed between any two adjoining rolling elements, and a coupler member connecting the separators to one another, the separator being made even in thickness at a zone over which a sliding contact point thereof with the associated rolling element changes place when the separator moves through the curvilinear passage, the coupler member being made in the form of a strip kept substantially constant in cross section throughout the overall length to bend uniformly with a fixed radius of curvature when moving in the curvilinear passage, and wherein the coupler member in the curvilinear passage travels along a desired curve having a radius of curvature, which is less than a radius of curvature of a locus of center of the rolling element, but larger than a radius of curvature of a locus of the sliding contact point of the separator with the associated rolling element, which will change place when the separator moves through the curvilinear passage.
The slider has a carriage and end caps attached to forward and aft ends of the carriage, each to each end. The linear passage includes a load raceway defined between a raceway groove formed in the carriage and a raceway groove formed on the track rail, and a return passage made in the carriage in parallel with the load raceway, while the curvilinear passage is composed of turnarounds formed in the end caps, each to each cap. The recirculating passage has incorporated with not only the rolling elements running through there, but also separators connected together to the coupler member to space any two adjoining rolling elements apart away from each other thereby keeping them against direct contact with each other.
The separators are joined together with the coupler member into the form of a kind of chain.
According to one aspect of the present invention, a linear motion guide unit with a separator coupler is disclosed in which the slider includes therein a carriage and end caps attached to forward and aft ends of the carriage, each to each end, the linear passage is composed of a load raceway defined between a raceway groove formed in the carriage and a raceway groove formed on the track rail, and a return passage made in the carriage in parallel with the load raceway, while the curvilinear passage is composed of turnarounds formed in the end caps, each to each cap.
According to another aspect of the present invention, a linear motion guide unit with a separator coupler is disclosed in which the separator coupler is composed of a pair of coupler members arranged to flank on radially opposite sides of any rolling element, each to each side, and joined together with the separators.
According to another aspect of the present invention, a linear motion guide unit with a separator coupler is disclosed in which the rolling element is a ball, and the coupler members arranged to flank on radially opposite sides of any rolling element define, in combination with any two adjacent separators, substantially round windows to accommodate therein the balls, each in each window. As an alternative, the rolling element is any one of a ball and a roller, and the coupler members arranged to flank on radially opposite sides of any rolling element define, in combination with any two adjacent separators, substantially rectangular windows to accommodate therein the rolling elements, each in each window.
According to a further another aspect of the present invention, a linear motion guide unit with a separator coupler is disclosed in which the separators extend radially inwardly of the curvilinear passage, with ranging from a place lying on the desired curve for the coupler member to an innermost end thereof coming into sliding engagement with a radially inside surface of the curvilinear passage, thereby helping ensure that the coupler member travels along the desired curve throughout the curvilinear passage.
According to another aspect of the present invention, a linear motion guide unit with a separator coupler is disclosed in which the separators each have inside and outside parts that extend in radially opposite direction of the curvilinear passage in symmetry with respect to a lengthwise centerline of the coupler member.
According to another aspect of the present invention, a linear motion guide unit with a separator coupler is disclosed in which the separators each made even in thickness in cross section throughout an overall width spanning between a radially inside surface and a radially outside surface in the recirculating passage. As an alternative, the separators each are made thickened in cross section only at an innermost end thereof near the radially inside surface in the recirculating passage, compared with other residual area of the separator. Moreover, the separators each may be made thickened in cross section not only at an innermost end thereof near the radially inside surface in the recirculating passage, but also at an outermost end thereof near the radially outside surface in the recirculating passage in such a configuration fitting over and conforming to the associated rolling element, with leaving a zone over which a sliding contact point thereof with the associated rolling element changes place when the separator moves through the curvilinear passage.
A further another aspect of the present invention, a linear motion guide unit with a separator coupler is disclosed in which there is provided a retainer band to keep in place not only the rolling elements but also a coupler chain of the coupler member connected with the separators against falling out of the slider even after the slider has been disassembled from the track rail.
With the linear motion guide unit constructed as stated earlier, the rolling elements are spaced apart away from each other with the separators that are each interposed between any two adjoining rolling elements and also joined together by means of the coupler member. Nevertheless, the coupler member may be less subject to deformation even the construction that the rolling elements turn about with a small radius of curvature or the turnaround is made small in the radius of curvature. Thus, the rolling elements are allowed to run smoothly through the curvilinear passage in the recirculating passage or the turnaround formed in the end cap, with being less subject to resistance due to the coupler member. As any rolling element comes into only point contact with the associated separator, both the rolling element and the separator may be less subject to wear, consequently improved in running performance in the recirculating motion. Moreover, since the sliding contact point of the separator with the associated rolling element may easily change place when the rolling element goes ahead through the turnaround, the rolling elements are allowed to run smoothly through the recirculating passage, especially the curvilinear passage in the turnaround without undergoing the resistance owing to the coupler member.
According to the linear motion guide unit constructed as described above, the coupler member experiences less deformation even the turnaround is small in radius of curvature. Thus, the rolling elements are allowed to run smoothly through the curvilinear passage in the recirculating passage or the turnaround formed in the end cap, with being less subject to resistance due to the coupler member. In particular, the rolling elements, as less subject to wear, are allowed continuing to keep high running performance. Thickening the separator at either any one or both of its innermost end near the radially inside surface in the recirculating passage and its outermost end near the radially outside surface in the recirculating passage, moreover, helps reduce wear of the separator and also keep in place the associated rolling element.
Other objects and features of the present invention will be more apparent to those skilled in the art on consideration of the accompanying drawings and following specification wherein are disclosed preferred embodiments of the invention with the understanding that such variations, modifications and elimination of parts may be made therein as fall within the scope of the appended claims without departing from the spirit of the invention.